Synthesis, X-ray structure and spin crossover in the triple-decker complex [(η5-C5Me5)Cr(µ2:η5-P5)Cr(η5-C5Me5)]+[A]–(A = PF6, SbF6)

Abstract

The triple-decker chromium complexes [(η⁵-C₅Me₅)Cr(µ²:η⁵-P₅)Cr(η⁵-C₅Me₅)]⁺[A]^–(A = PF₆, SbF₆) can be prepared in high yield by oxidation of [(η⁵-C₅Me₅)Cr(µ²:η⁵-P₅)Cr(η⁵-C₅Me₅)] with either [Fe(η⁵-C₅H₅)₂]⁺[A]^–(A = PF₆, SbF₆); the single crystal X-ray structure determination for [(η⁵-C₅Me₅)Cr(µ²:η⁵-P₅)Cr(η⁵-C₅Me₅)]⁺[SbF₆]^– reveals that the Cr–Cr separation is 3.185(8)Å which is 0.456 Å longer than in the neutral complex; magnetic susceptibility studies show that these 26-electron multidecker cations in these salts undergo spin crossover at 33 and 23 K respectively.